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inkyvoydBest ResponseYou've already chosen the best response.0
if y=3x^2+2x and dx/dt=4, find dy/dt when x=3 My answer: dy/dt=24x+8; dy/dt=80. Can someone please check this? THanks!
 one year ago

tamtoanBest ResponseYou've already chosen the best response.0
isn't it dy/dt = 6x dx/dt + 2dx/dt ? can someone check this ?
 one year ago

zepdrixBest ResponseYou've already chosen the best response.2
Yah @tamtoan is on the right track there,\[\huge y=3x^2+2x\]If we take the derivative with respect to TIME, we'll get,\[\huge \color{#CC0033}{\frac{dy}{dt}}=6x\color{#F35633}{\frac{dx}{dt}}+2\color{#F35633}{\frac{dx}{dt}}\]And they gave us information about dx/dt and x.\[\huge \color{#CC0033}{\frac{dy}{dt}}=6(3)(\color{#F35633}{4})+2(\color{#F35633}{4})\]Understand where those numbers are coming from?
 one year ago

inkyvoydBest ResponseYou've already chosen the best response.0
Uh, the answer is defienitely 80, because I just submitted te assignment. Let me go over what happened though
 one year ago

inkyvoydBest ResponseYou've already chosen the best response.0
Yeah, @zepdrix , you have the dx/dt because x is a function of t; @tamtoan didn't have that. Thanks.
 one year ago

zepdrixBest ResponseYou've already chosen the best response.2
Tam had the same thing, he just didn't plug in the x and dx/dt values for you :D
 one year ago

inkyvoydBest ResponseYou've already chosen the best response.0
Oh he did :S. Well, thanks for helping out!
 one year ago
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